Wheels on the Bus, one of the first apps I reviewed for GeekDad back in 2009, has just turned 4 years old. The app remains a great example of digital play for young children on touchscreen devices. Of course, we have come a long way in that short time, but the use of color, the limited touch points, the quality of the music and the sense of narrative all point to why Duck Duck Moose has grown in the way that it has.